China, People's Republic of : Piloting Innovative Flash Flood Early Warning Systems in Selected River Basins

Agriculture, natural resources and rural development / Rural flood protection - Rural water policy, institutional and capacity development - Water-based natural resources management

Floods, together with storms, account for 76% of natural hazards that have occurred globally and caused 87% of economic loss due to such disasters from 2006 to 2015. Water crisis, climate change, and extreme weather events are identified as the top three global threats over the next 10 years. Historically, floods are the costliest natural hazard-induced disaster in the PRC. Annual economic loss due to floods in the PRC is estimated at about $20 billion, and the loss trend has been escalating by 7% since 1990. From 1980 to 2016, the PRC suffered from flood events that resulted in an annual average of 1,500 deaths and affected about 66 million people. Frequent flood disasters throughout history have setback the socioeconomic development of the PRC and now hinder the achievement of the sustainable development goals.

An important lesson learned from recent flood events in 2016 and 2017, particularly along the Yangtze river basin, is that majority of flood damage does not come from the main stem river but from small-to-moderate sized river sub-basins and mostly associated with flash flood events. Rapid urbanization of small villages and towns in these sub-basins has triggered flash floods and landslides; these disaster events are not regarded as among the government's priorities in the past. Throughout the middle and lower Yangtze river basin, flood emergencies rose at more than 3,300 locations during the 2016 floods, resulting to over $40 billion in economic loss. Of those, over 3,200 flash flood events were reported to occur on small tributaries which are generally provided with lower standards of flood protection or where standards have not kept pace with the rapid rate of development. The excessive damage was attributed to the lack of spatial or temporal coverage of, and the gaps in end-to-end early warning system that involves six interactive elements: (i) risk knowledge; (ii) monitoring and data acquisition; (iii) forecasting and warning; (iv) dissemination and communication; (v) information type and reliability; and (vi) response capacity.

In 2006, the State Council of the PRC launched the national flash flood disaster prevention plan with different targets including strengthening the monitoring and early warning system and enhancing the preparedness and emergency response capacity at national and local levels. The government has invested about CNY22.5 billion in national flash flood disaster prevention and mitigation projects during 2006 2015. As a result, the average annual flash flood disaster-related fatalities have remarkably been reduced from 1,100 to 400 persons during 1990 2015. The efforts to further reduce human casualties and economic loss due to flash floods in the PRC should consider a variety of factors including land use changes; flood exposures; climate change; uncertainty of temporal and spatial distribution of flash floods; and accuracy in early warning and localization of early warning system for emergency response with community empowerment.

Forecasting and early warning is considered the most effective measure to save lives and reduce the damage from flash floods. While the PRC is pioneering flood preventive measures, the forecasting and early warning system in the PRC in general, is still at its primary stage of development. The challenges in establishing a reliable flash flood early warning system in the PRC are: (i) the national program is being implemented in a coarse spatial scale and has not yet been specialized for a large number of small river sub-basins, and scattered villages or towns in remote geographical settings; (ii) weather forecasts are becoming more detailed and accurate and yet to be employed to increase lead-time in flood early warning; (iii) a large number of small sub-basins are not being monitored by hydrological and meteorological stations, which made it difficult to develop a reliable localized flash flood early warning system; (iv) self-help and mutual-help conditions are yet to be promoted with awareness campaign and capacity building activities at grassroot communities to improve the effectiveness of the early warning system; and (v) institutional capacity in flood forecasting and early warning at local governments is not sufficient. Rapid socioeconomic development on the flash flood prone areas have called for a reliable flash flood forecasting and early warning system with strong engagement of the local communities.

In December 2017, the Ministry of Water Resources issued the National Flash Flood Disaster Prevention Project Implementation Plan (2017 2020), which prioritizes flash flood monitoring and warning provisions nationwide, reflecting the lessons learned from the recent disasters. The government has requested ADB for a technical assistance in piloting a standalone flash flood early warning system suitable for small river sub-basins to be a benchmark for future investment under the national plan. The TA aims to pilot a standalone end-to-end flash flood early warning system, which is compatible to small sub-basins. The TA will demonstrate new approach, methodology, and technology to (i) increase warning accuracy and its effectiveness in evacuation and emergency response; (ii) extend the lead time of warning to provide more time to local residents to save valuables and their own lives; (iii) support the local governments and communities through the establishment of decision support system in emergency response; and (iv) improve information dissemination, and promote community-based early warning. The pilots will be implemented in Xinyu City in Jiangxi Province and Luanchuan County in Henan Province, both suffered serious flash floods in the past. More than 100 villages in the mountains of Luanchuan County in Henan Province heavily suffered flash floods in 2016. These villages are in the corridor of Yangtze River. During the past flash flood events in the pilot areas, centralized early warning information could not reach all the communities in a reliable manner; the early warning information given to the public was too coarse as there are no hydro-meteorological observation stations, it was difficult to make evacuation order; the time available to the communities for evacuation was too short, people either did not evacuate or have been mistakenly evacuated; and communities did not know when and how to evacuate, resulting in huge loss and damage. The TA will help upgrade and strengthen the application of flash flood early warning system in the PRC, mainly in many isolated or remote small villages, which have not benefitted from the centralized early warning system.

Flash flood early warning in selected river sub-basins upgraded

Capacity development for flash flood emergency response at local level enhanced

Knowledge on flash flood early warning system disseminated